When we are dealing with suffering, we are dealing with “the stuff that makes up human experience”. Because this is so, we cannot have a strategy for overcoming suffering that is divorced from the reality of suffering. Reality and strategy cannot be separated.
I will give you a simple analogy. If you need to shop for groceries, you need a strategy for how to get to the supermarket. This strategy needs to be informed by the actual location of the supermarket. Reality and strategy need to go hand in hand. You could make a similar argument for almost anything we do in life. The spiritual life is no exemption.
A big part of the problem is that we already have an idea of the nature of existence. We are not blank slates on which a strategy can be applied. In particular, we automatically have a sense of a self. If all you have is a strategy, that strategy will act in the service of your sense of self. Let’s see how this might work.
The contemplation of impermanence is one of the main “strategies” for spiritual growth advocated in the suttas. Even if we assume a self, this strategy would actually work for a while. Most things in our experience are impermanent, and it’s obvious that these things have nothing to do with a permanent essence. If we see the true nature of these impermanent phenomena, we might be able to abandon craving and attachment to them, and thereby approach the supposed deeper reality of an essential self. It is not unreasonable to think that you might be able to realise this self through such a strategy.
In practice this would mean seeing the sensual world as impermanent and problematic. You then abandon attachment to this world and enter the world of samādhi. This world of samādhi has all the characteristics that fulfil your deepest desires: a perfectly content state of nondual bliss. And, crucially, it seems to align perfectly with your sense of self. It seems obvious that this state will carry on indefinitely after you die. There is no motivation for you to go any deeper. You have reached a supermarket, but unknown to you, it happens to be the wrong one.
So, what you need is a corrective to your powerful disposition to experience a sense of self. You need something to guide you to go beyond your own bias. This is where the Buddha’s more ontologically oriented statements come in. Even if you have roughly the right strategy, you need clarity about the nature of reality to ensure that you use that strategy wisely. Only in this way will you end up at the right supermarket.
Strategy and an accurate description of certain aspects of reality must go hand-in-hand.
We just need to be careful with what we mean by physicalism. If you have an idea of physicalism that is compatible with rebirth, then I have no problems with it. In the end, I prefer to remain philosophically agnostic.